Non-aqueous electrolyte primary batteries using lithium as anode active material and carbon fluoride, manganese dioxide or the like as cathode active material have already been put to practical use and are increasingly used as power sources for various types of electronic equipments. Such non-aqueous electrolyte type batteries using lithium for anode are specified by high voltage and high energy density, and in view of such specific advantages, intense studies have been and are made for the development of secondary batteries using non-aqueous electrolyte. Nevertheless, no successful attainment has yet been made for the practical application of such secondary batteries, mostly due to the failure in overcoming the problems of short charge and discharge life and low charging and discharging efficiency, for which anode is greatly responsible.
In the case of lithium anode made by press bonding a metallic lithium plate to a screen-like current collector metal such as nickel, which is used in primary batteries, it is difficult to let lithium, which has been dissolved into the electrolyte on discharging, separate out to restore its original plate-like form on charging. For instance, lithium is precipitated irregularly in the form of dendrite on charging and such precipitated lithium drifts away from the electrode plate and no longer serves as active material, or the lithium which was precipitated in the form of dendrite may pass through the separator and come into contact with the cathode to cause short-circuiting.
Various attempts have been made for overcoming such problems of lithium anode. It is considered as the most prospective method to use as anode material a certain type of metals or alloys which have the specific property to absorb or take up lithium ions in the electrolyte on charging and desorb absorbed lithium as ions into the electrolyte on discharging.
As such type of anode materials, there are known aluminum (U.S. Pat. No. 3,607,413), silver (Japanese Patent Application Laid-Open No. 7386/81, U.S. Pat. No. 4,316,777, and U.S. Pat. No. 4,330,601), lead (Japanese Patent Application Laid-Open No. 141869/82), tin, tin-lead alloy, etc. These materials, however, have the defect that the increase of lithium absorption rate with charging causes fine powdering of the anode material to make it unable to maintain the shape of electrode.
On the other hand, it has found that the alloys proposed by the present inventors in PCT/JP 84/00086 and PCT/JP 84/00088, that is, the alloys comprising cadminum and/or zinc as essential ingredients and further containing at least one member selected from the group consisting of lead, tin, indium and bismuth are relatively high in the rate of absorption of lithium and also excellent in charge/discharge reversibility and thus have a bright prospect for practical use as a rechargeable anode material.
It was found, however, that the following problems arise when a battery is actually assembled by using said alloys as anode material. When assembling a battery, the anode is usually used in a charged state, that is, in a lithium-absorbed state, but when lithium is absorbed in said alloys, they become hard and brittle and lose flexibility. Therefore, especially when cathode and anode are laminated with a separator therebetween and wound up spirally to constitute a spiral electrode plate, the anode tends to be cracked to make it unable to obtain a desired electrode capacity. Even in flat type cells using a flat plate-like anode, the anode can be cracked due to a shock of pressure at the time of sealing.
Assemblage of a battery by leaving the anode in a non-charged state, that is, in a non-lithium-absorbed state, is also difficult for the following reasons.
Intercalation compounds such as TiS.sub.2 and V.sub.6 O.sub.13 are known as cathode material for non-aqueous electrolyte secondary batteries. In case of using TiS.sub.2 for instance, there takes place at the cathode a reaction of the following formula: ##STR1## Since the discharging product Li.sub.x TiS.sub.2 or Li.sub.x V.sub.6 O.sub.13 is extremely unstable to water or oxygen, usually such compound as Li.sub.x TiS.sub.2 or Li.sub.x V.sub.6 O.sub.13 is not used but a compound such as TiS.sub.2 or V.sub.6 O.sub.13 is used as cathode material when assembling a battery. Further, it is difficult to chemically synthesize Li.sub.x TiS.sub.2 or Li.sub.x V.sub.6 O.sub.13. Since such compound is produced only when TiS.sub.2 or V.sub.6 O.sub.13 is electrochemically reduced according to the above-shown formula, a step for electrochemical reduction of TiS.sub.2 or V.sub.6 O.sub.13 is required for forming a cathode by using Li.sub.x V.sub.6 O.sub.13 or Li.sub.x TiS.sub.2. This makes the battery production process complicated and time-consuming. For these reasons, an oxide type compound such as TiS.sub.2 or V.sub.6 O.sub.13 is used instead of Li.sub.x TiS.sub.2 or Li.sub.x V.sub.6 O.sub.13 for forming cathode when assembling a battery.
Thus, it is necessary to use a lithium-absorbed anode for producing a desired battery. However, as mentioned below, such lithium-absorbed anode is devoid of flexibility and tends to be cracked in the course of production of the battery, causing a reduction of performance of the produced battery.